1. Field
An aspect of the present teachings relate to a substrate processing apparatus to thermally process substrates and/or form thin films on the substrates.
2. Description of the Related Art
Flat panel display devices are replacing cathode-ray tube display devices, due to their lighter weight and thinner profile. Flat panel display devices include liquid crystal display (LCD) devices and organic light emitting diode (OLED) display devices. Organic light emitting diode display devices provide improved brightness and viewing angles, as compared to liquid crystal display devices, and do not require backlight units, thereby realizing ultra-thin thicknesses.
In order to produce light, organic light emitting diode display devices use energy emitted from excitons, which are formed in an organic thin film when electrons injected from a cathode and holes injected from an anode are combined. Organic light emitting diode display devices are classified into passive-matrix OLEDs and active-matrix OLEDs, according to the driving method thereof. Active-matrix OLEDs have circuits that include thin film transistors (TFTs).
A flat panel display device is manufactured by forming a thin film, having electrical characteristics according to a determined pattern, on a substrate, using an organic material or an inorganic material. The thin film is then thermally processed. In this case, a thin film is mainly formed by a physical vapor deposition (PVD) method, such as a sputtering process, in which plasma is applied to a deposition target; or a chemical vapor deposition (CVD) method, such as an atomic layer deposition (ALD) process, in which reaction gases containing a source material are sprayed onto a substrate, to chemically form atomic layers of the source material on the substrate.
The chemical vapor deposition method produces thin films having excellent uniformity and step coverage, as compared to the physical vapor deposition method, and enables the simultaneous processing of a plurality of substrates. Therefore, it is widely used to form an amorphous silicon layer and an insulation layer, such as a nitride layer or an oxide layer.
In general, in order to simultaneously form thin films on a plurality of substrates, or to thermally process the substrates using the chemical vapor deposition method, a substrate processing apparatus includes a processing chamber for processing a plurality of substrates, a boat in which the substrates are stacked, a heater located outside the processing chamber to heat the interior of the processing chamber, and a feeder to move the boat into and out of the processing chamber.
However, since the heater is located outside of the processing chamber, and the processing chamber is generally large, so as to accommodate the boat, it is difficult to uniformly heat the interior of the processing chamber. In particular, substrates in the boat are not uniformly heated.